Relativistic and Theoretical Astrophysics

Start year
1988
Organizational Unit

Related grants:

    General
    Description

    Introduction

    Gravitational lenses are a powerful tool for Astrophysics and Cosmology. The goals of this project are: i) to obtain a robust determination of the Hubble constant from the time delay measured between the images of a lensed quasar; ii) to study the individual and statistical properties of dark matter condensations in lens galaxies from microlensing on the images of lensed quasars; iii) to study the unresolved structure of quasars (broad and narrow emission line and continuum emission regions) from induced variations by microlensing in the photometry of the lensed quasar images as well as in the profile of their emission lines; iv) to study the variation of dust extinction properties with redshift from the determination of extinction curves in lens galaxies; (v) to develop new numerical and statistical methods to study microlensing and (vi) to detect exoplanets through gravitational microlensing.

    Principal investigator
    1. We have introduced a new method to measure the masses of the supermassive black holes of the quasars based on the gravitational redshift of the ultraviolet lines of the iron (UV Fe III). The calculated masses are in agreement with the estimates obtained using the virial theorem.

    Related publications

    • Microlensing analysis of 14.5-year light curves in SDSS J1004+4112: Quasar accretion disk size and intracluster stellar mass fraction
      Context. The gravitational lens system SDSS J1004+4112 was the first known example of a quasar lensed by a galaxy cluster. The interest in this system has been renewed following the publication of r-band light curves spanning 14.5 years and the determination of the time delays between the four brightest quasar images. Aims. We constrained the
      Forés-Toribio, R. et al.

      Advertised on:

      11
      2024
      Citations
      0
    • The abundance of clustered primordial black holes from quasar microlensing
      While elementary particles are the favored candidate for the elusive dark matter, primordial black holes (PBHs) have also been considered to fill that role. Gravitational microlensing is a very well-suited tool to detect and measure the abundance of compact objects in galaxies. Previous studies based on quasar microlensing exclude a significant
      Muñoz, Jose A. et al.

      Advertised on:

      10
      2024
      Citations
      0
    • Revealing the inner workings of the lensed quasar SDSS J1339+1310: Insights from microlensing analysis
      Aims. We aim to unveil the structure of the continuum and broad-emission line (BEL) emitting regions in the gravitationally lensed quasar SDSS J1339+1310 by examining the distinct signatures of microlensing present in this system. Our study involves a comprehensive analysis of ten years (2009–2019) of photometric monitoring data and seven
      Fian, C. et al.

      Advertised on:

      9
      2024
      Citations
      0
    • First Direct Evidence for Keplerian Rotation in Quasar Inner Broad-line Regions
      We introduce a novel method to derive rotation curves with light-day spatial resolution of the inner regions of lensed quasars. We aim to probe the kinematics of the inner part of the broad-line region by resolving the microlensing response—a proxy for the size of the emitting region—in the wings of the broad emission lines. Specifically, we assess
      Fian, C. et al.

      Advertised on:

      9
      2024
      Citations
      2
    • Single-epoch and Differential Astrometric Microlensing of Quasars
      We propose and discuss a new experimental approach to measure the centroid shift induced by gravitational microlensing in the images of lensed quasars (astrometric microlensing). Our strategy is based on taking the photocenter of a region in the quasar large enough as to be insensitive to microlensing as reference to measure the centroid
      Forés-Toribio, R. et al.

      Advertised on:

      7
      2024
      Citations
      0
    • Changing Look of the Optical Spectrum of the MeV Blazar PKS 0446+112 (4FGL J0449.1+1121)
      Following the high activity of the γ-ray Fermi source 4FGL J0449.1+1121 (PKS 0446+112), possibly associated with a IceCube neutrino event IC-240105A, we obtained optical spectroscopy with the Gran Telescopio Canarias of the counterpart. We detect a clear emission line at 3830 Å identified as Lyα that confirms the redshift of source at z = 2.153
      Paiano, Simona et al.

      Advertised on:

      6
      2024
      Citations
      3
    • Quasar Microlensing Statistics and Flux-ratio Anomalies in Lens Models
      Precise lens modeling is a critical step in time delay studies of multiply imaged quasars, which are key for measuring some important cosmological parameters (especially H 0). However, lens models (in particular those semi-automatically generated) often show discrepancies with the observed flux ratios between the different quasar images. These flux
      Mediavilla, E. et al.

      Advertised on:

      4
      2024
      Citations
      1
    • Probing the structure of the lensed quasar SDSS J1004+4112 through microlensing analysis of spectroscopic data
      Aims: We aim to reveal the sizes of the continuum and broad emission line (BEL) emitting regions in the gravitationally lensed quasar SDSS J1004+4112 by analyzing the unique signatures of microlensing in this system. Through a comprehensive analysis of 20 spectroscopic observations acquired between 2003 and 2018, we studied the striking
      Fian, C. et al.

      Advertised on:

      2
      2024
      Citations
      8
    • Black hole masses for 14 gravitationally lensed quasars
      Aims: We have estimated black hole masses (M BH) for 14 gravitationally lensed quasars using Balmer lines; we also provide estimates based on MgII and CIV emission lines for four and two of them, respectively. We compared these estimates to results obtained for other lensed quasars. Methods: We used spectroscopic data from the Large Binocular
      Melo, A. et al.

      Advertised on:

      12
      2023
      Citations
      2
    • Revealing the structure of the lensed quasar Q 0957+561. III. Constraints on the size of the broad-line region
      Aims: Our aim is to examine the size, kinematics, and geometry of the broad-line region (BLR) in the double-lensed quasar Q 0957+561 by analyzing the impact of microlensing on various rest-frame ultraviolet broad-emission lines (BELs). Methods: We explore the influence of intrinsic variability and microlensing on the C IV, C III], and Mg II
      Fian, C. et al.

      Advertised on:

      10
      2023
      Citations
      9
    • Constraints on the Abundance of Primordial Black Holes from X-Ray Quasar Microlensing Observations: Substellar to Planetary Mass Range
      We use X-ray observations of quasar microlensing (sensitive to smaller compact objects than in the optical) to study the possible presence of a population of low mass black holes (BHs; from ~10 -3 M ⊙ to 10 -1 M ⊙) in lens galaxies. We compare these observations with microlensing magnification simulations of a mixed population of stars and BHs plus
      Esteban-Gutiérrez, A. et al.

      Advertised on:

      9
      2023
      Citations
      9
    • Long-term optical spectral monitoring of a changing-look active galactic nucleus NGC 3516. II. Broad-line profile variability
      Context. We analyze the broad Hβ line profile variability of a "changing look" active galactic nucleus (CL-AGN) NGC 3516 over an extensive period of 25 years (from 1996 to 2021). The observed change in the broad line profile may indicate a change in the geometry of the broad line region (BLR). The main objective is to follow and understand the
      Popović, Luka Č. et al.

      Advertised on:

      7
      2023
      Citations
      10
    • The spectra of IceCube Neutrino (SIN) candidate sources - III. Optical spectroscopy and source characterization of the full sample
      A correlation between astrophysical high-energy neutrinos and blazars has been suggested by various authors. In particular, a likely association between IceCube events and intermediate- and high-energy peaked BL Lac objects has led to a sample of 47 objects having a high probability of being neutrino sources. In the first paper of this series we
      Paiano, Simona et al.

      Advertised on:

      5
      2023
      Citations
      11
    • Fast Multipole Method for Gravitational Lensing: Application to High-magnification Quasar Microlensing
      We introduce the use of the fast multipole method (FMM) to speed up gravitational lensing ray tracing calculations. The method allows very fast calculation of ray deflections when a large number of deflectors, N *, are involved, while keeping rigorous control on the errors. In particular, we apply this method, in combination with the inverse
      Jiménez-Vicente, J. et al.

      Advertised on:

      12
      2022
      Citations
      15
    • Revealing the structure of the lensed quasar Q 0957+561. II. Supermassive black hole mass via gravitational redshift
      Aims: We intend to use the impact of microlensing on the Fe III λλ2039−2113 emission line blend along with a measure of its gravitational redshift to estimate the mass of the quasar's central supermassive black hole (SMBH). Methods: We fit the Fe III feature in multiple spectroscopic observations between 2008 and 2016 of the gravitationally lensed
      Fian, C. et al.

      Advertised on:

      11
      2022
      Citations
      5
    • Virial theorem in clusters of galaxies with MOND
      A specific modification of Newtonian dynamics known as MOND has been shown to reproduce the dynamics of most astrophysical systems at different scales without invoking non-baryonic dark matter (DM). There is, however, a long-standing unsolved problem when MOND is applied to rich clusters of galaxies in the form of a deficit (by a factor around two)
      López-Corredoira, M. et al.

      Advertised on:

      12
      2022
      Citations
      4
    • A Mass Model for the Lensing Cluster SDSS J1004+4112: Constraints from the Third Time Delay
      We have built a new model for the lens system SDSS J1004+4112 including the recently measured time delay of the fourth quasar image. This time delay has a strong influence on the inner mass distribution of the lensing cluster (ρ ∝ r -α ) allowing us to determine $\alpha ={1.18}_{-0.03(-0.18)}^{+0.02(+0.11)}$ at the 68% (95%) confidence level in
      Forés-Toribio, R. et al.

      Advertised on:

      9
      2022
      Citations
      14
    • Limiting the Abundance of LIGO/Virgo Black Holes with Microlensing Observations of Quasars of Finite Size
      We present a simple but general argument that strongly limits the abundance of primordial black holes (PBHs) (or other unknown population of compact objects) with masses similar to those determined by LIGO/Virgo from BH binary mergers. We show that quasar microlensing can be very sensitive to the mass of the lenses, and that it is able to
      Esteban-Gutiérrez, A. et al.

      Advertised on:

      4
      2022
      Citations
      6
    • On the orbital velocity of isolated galaxy pairs: II accurate MOND predictions
      Examining a catalogue of isolated galaxy pairs, a preferred orbital intervelocity of ~ 150 km s -1 was recently reported. This discovery is difficult to reconcile with the expectations from Newtonian numerical simulations of cosmological structure formations. In a previous paper, we have shown that a preferred intervelocity for galaxy pairs is
      Scarpa, Riccardo et al.

      Advertised on:

      5
      2022
      Citations
      5
    • HARMONI view of the host galaxies of active galactic nuclei around cosmic noon. Resolved stellar morpho-kinematics and the M<SUB>BH</SUB> − σ<SUB>⋆</SUB> relation
      Context. The formation and evolution of galaxies appear linked to the growth of supermassive black holes, as evidenced by empirical scaling relations in nearby galaxies. Understanding this co-evolution over cosmic time requires the revelation of the dynamical state of galaxies and the measurement of the mass of their central black holes (M BH) at a
      García-Lorenzo, B. et al.

      Advertised on:

      3
      2022
      Citations
      1

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